Objective: Mental overactivity has been widely implicated in the development and maintenance of insomnia, making the accurate and valid measurement of cognitive variables of some importance. The purpose of this study was to investigate the psychometric properties of two existing attributional scales.
Methods: Data are presented from 178 clinic attending insomniacs who completed the Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS) and the Sleep Disturbance Questionnaire (SDQ). Standard procedures for the psychometric evaluation of scales were adopted.
Results: The internal consistency of the DBAS (30 items) was reasonable (Cronbach's alpha = 0.72); however, a revised ten-item short form (DBAS-10) demonstrated a more robust principal component structure than the original scale (three relatively "pure" factors explained 55% of the variance). The derived subscales achieved satisfactory internal consistency, and the DBAS-10 demonstrated treatment-related measurement sensitivity. The DBAS-10, nevertheless, correlated highly (r = 0.826) with the DBAS. A four-factor solution for the SDQ is also presented (61% explained variance) with alpha = 0.67. Internal consistency of these subscales ranged from 0.59 to 0.82. The association between the SDQ and DBAS-10 was modest (r = 0.28), suggesting that the scales have some independence.
Conclusions: The scales offer potential for clinical and research work on insomnia and possible applications are discussed.